Hand vibrator for spark discharge metal depositing



Dec. 10, 1968 w. B. SHAFF'ER 3,415,971

HAND VIBRATOR FbR SPARK DISCHARGE METAL DEPOSITING Filed Dec. :51, 1964 v// 4 I 1; i I ,/l 4

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United States Patent HAND VIBRATOR FOR SPARK DISCHARGE METAL DEPOSITING William B. Shaffer, Grosse Pointe Woods, Mich., assignor t0 Elox Corporation, Troy, Mich., a corporation of Michigan Filed Dec. 31, 1964, Ser. No. 422,845 2 Claims. (Cl. 219-76) ABSTRACT OF THE DISCLOSURE A spark discharge apparatus includes a vibrator in a hand held housing. The vibrator motor has a spring biased channel shaped lever with an armature mounted in and insulated from the lever to prevent eddy current flow therethrough. The lever is pivoted from a raised shoulder at one end and an erodable electrode is connected to the opposite end of the lever and projects outside the housing. A capacitive discharge circuit connects the electromagnet and the electrode with a DC. source such that the circuit acts as a relaxation oscillator for vibrating the electrode and depositing metal on the workpiece as the arc discharges.

This invention relates to apparatus for depositing on a metal surface a coating of a similar or different metal by the spark discharge process and more specifically, relates to a new and improved hand vibrator unit for use in conjunction therewith.

The apparatus disclosed herein is adapted for the performance of a variety of operations depending upon the electrical parameters used and the material of the electrode selected. The apparatus is utilized for hard facing applications on tools, forging dies, punching dies and the like in which case tungsten carbide electrodes are ordinarily used. Identification marking can also be accomplished by spark depositing with an electrode of copper base alloys, silver base alloys and others being used with the selection dependent upon the deposited mark color desired. Additionally, the apparatus may be used for anti-corrosive facing for placing anti-acid and antialkali protective layers on metallic objects.

A major problem encountered in the spark depositing field is the provision of a hand vibrator unit with simplified mechanism and parts which are not subject to rapid wear or deterioration in use. It is further necessary that the vibration rate imparted by the hand nut to the electrode shall be precisely controllable and in a manner which permits ready variation as required by the specific application. One critical action involved in the spark discharge depositing operation is that of achieving a rapid and abrupt action required to remove the electrode tool from contact with the workpiece at each spark depositing contact, This can be accomplished with a satisfactory degree of success and commercial practicality only when certain teachings of the present invention are followed.

A broad object of this invention is to provide an electro-mechanical hand vibrator which may be moved in a manner hereinafter to be described across the surface of a workpiece to achieve metal deposition with the precisencss of control and effectiveness required.

It is a further object of this invention to provide an improved hand vibrator unit in which the electro-mechanical action is achieved through a novel combination of elements particularly in the electro-magnetic assembly to give a maximum rate of electrode vibration with a positive electrode withdrawal movement and with minimal heat generation within the hand tool.

The aforementioned and other objects together with the novel features and advantages of the invention will Patented Dec. 10, 1968 "ice become evident as the description proceeds in conjunction with the accompanying drawings.

FIGURE 1 is an electrical schematic diagram simplified to illustrate the manner in which the spark depositing apparatus operates.

FIGURE 2 is a View of the hand vibrator unit with cover removed and parts broken away to best illustrate its parts and mode of operation.

FIGURE 3 is a sectional view along the line AA of FIGURE 2 to disclose the mode of mounting utilized for the armature carrying member.

Reference is hereby made to US. Patent 3,098,150, entitled Spark Discharge Metal Depositing Apparatus, issued on July 16, 1963 to Kiyoshi Inoue, which patent illustrates the basic theoretical considerations and mode of operation of a metal depositing apparatus of the spark discharge type.

FIGURE 1 shows DC source 10 which may be embodied commercially as an AC power input together with full wave rectifier in a manner well known in the art. A capacitor 12 is shown connected across the spark depositing gap which comprises electrode tool 14 and workpiece 16. It will be observed that the electrode tool 14 is spaced and held manually at an optimum gap distance preliminary to and during the metal depositing cycle. The polarity of the electrode tool 14 is normally positive while that of the workpiece is maintained negative. To achieve the required vibrating action of the electrode tool 14 relative to the workpiece 16, a winding 18 is connected in series between the positive terminal of DC source 10 and the terminal of capacitor 12 as illustrated. Winding 18 constitutes the electromagnetic coil winding as further illustrated in physical detail in FIGURE 2 and its function will be explained in the following section entitled Description of Operation.

FIGURE 2 shows the tool utilized which is in the basic configuration of a hand operated tool. The casing 20 is provided as shown to enclose the electromagnetic assembly which is mounted on bracket 21 secured to the inner wall of casing 20. This assembly includes winding 18, a core 22 of the well known E-core type of construction and including pole faces 24 and 26. Core 22 is mounted to bracket 21 through screws 28a-d as illustrated. The movable armature 30 is carried by a channel shaped lever 32 and is maintained in operative spaced proximity to pole faces 24 and 26. Channel shaped lever 32 is a three sided structure with its open side located at the top to provide maximum rigidity and for other purposes to be explained hereinafter. The pivotal mounting for lever 32 is provided near its righthand end by a pin 34 journalled through a raised shoulder portion 36 at the righthand end of lever 32. To achieve maximum attractive effect by core 22 and its pole faces 24, 26 in the energized condition of coil 18, the placement of the pivotal mounting afforded by pin 34 is located at a point spaced from and substantially in the line with the upper portion of armature 30 and pole faces 24, 26. This affords uniform spacing to provide for maximum magnetic attraction of armature 30 which is of particular importance when we consider that the abrupt withdrawal action of the electrode tool is a matter of prime concern in the spark depositing process. Lever 32 further has mounted at its lefthand end an electrode holder 38 which is rigidly mounted at its upper end to lever 32. The electrode tool 14 is slidably inserted in electrode holder 38 and held in place by set screw 40 which set screw may be periodically loosened to permit selective change in electrode length as the process is carried on and as electrode wear progresses. A portion of the power lead to the electrode is indicated by numeral 15 with its terminal 44 connected to the upper portion of electrode holder 38 by locking nut 45 as indicated. Electrical insulation is provided between lever 32 and electrode holder 38 by washer 47 and sleeve 49. A means is further mounted on a bent portion 43 of bracket 21 for providing adjustment of the gap between pole faces 24, 26 and armature 30. This means includes a biasing spring 46 which provides a resilient force against the lefthand end of lever 32 urging it downwardly and tending to bring electrode 14 into contact with workpiece 16. Spring 46 is confined between spacer 50 and knurled adjusting nut 48. Adjusting nut 48 is fixed to the lower end of stud 52 which stud threadably engages nut 54 at its upper end. The aforementioned gap is narrowed by the clockwise rotation of adjusting nut 48 and, alternately, widened by its counterclockwise rotation. Nut 54 serves the function of locking the adjustment against the effect of vibration during operation.

FIGURE 3 shows the detail of lever 32 with its uppermost side open and the manner in which it is pivotably mounted to bracket 21 upon pin 34. A screw 35 is used to fix pin 35 to bracket 21 as shown with pin 34 journalled through raised shoulder portion 36 of lever. As is best shown in FIGURE 2, the axis of pin 34 is substantially parallel to the surface of armature 30 for reasons herein before indicated.

Description of operation The connection of DC source across capacitor 12 and the gap between electrode 14 and workpiece 16 provides a relaxation oscillator type of circuit in which there is a charging current flow provided to charge capacitor 12 which capacitor is then discharged across the gap. At the same time, current passes through energized coil 18 in such a manner as to cause armature 30 to be attracted toward pole faces 24, 26. However, the magnetomotive force developed by energizing of coil 18 reaches a maximum after the contacting points between electrode 14 and workpiece 16 have been heated sufficiently to cause a momentary fusion and reduce the contact resistance. Thus, there is an abrupt and forcible upward movement caused by the attraction of armature 30 to remove the electrode 14 from the workpiece 16. With the contact thus interrupted, short-circuiting of condenser 12 is ended and recharge of condenser 12 follows. In the recharging of condenser 12, the inductive reactance of coil 18 which tends to maintain a current flow in itself provides an additional self-inductance voltage which is additive to the voltage of source 10 in charging the condenser. Consequently, as condenser 12 is recharged, the coil 18 becomes deenergized. This permits the force asserted by spring 46 against channel member 32 to become effective to again force the electrode 14 back downwardly toward contact with the workpiece 16. Each time the electrode approaches the workpiece, a spark is caused to pass across the gap between electrode and workpiece to initiate a following cycle of operation. The resulting action is a continuous vibratory action between electrode 14 and workpiece 16 in which the electrode and workpiece serve as effectual contacts of electrical switching means to control the successive energization and deenergization of coil 18 and its associated capacitor 12. During this action, the electrode 14 erodes in such a manner as to deposit metal on the workpiece 16 thus requiring progressive advancement of electrode 14 in its holder 38. The frequency of electrode vibration may be selectively adjusted and controlled by choice and adjustment of the pressure of spring 46, the value of inductance of coil 18, and other electrical parameters of the circuit. Vibrational frequencies may be obtained of the order of 150-400 cycles per second or even greater. It is essential that the return force asserted by the pole faces 24, 26 upon armature 30 and its associated member 32 be as fast acting and positive as possible to prevent adherence of the electrode to the workpiece and further to obtain the maximal vibrational frequency that may be possible. A further consideration is that the armature 30 which is normally a slug of a laminated type ferromagnetic material must be mounted in lever 32 so as to eliminate the possibility of any eddy current flow between it and member 32 which would cause substantial heating and loss of electrical energy. This mounting is satisfactorily provided only by a means which does not require perforation of the lever 32 or armature 30 and fastening by any electrically conductive means. Lever 32 is preferably made of a metallic material which is of particular advantage in dissipating whatever heat may be generated in the armature 30. The mounting of armature 30 in channel 32 must be accomplished by a means interior to that member and is accomplished in the present instance by an adhesive material such as a layer of epoxy resin 31 which is used to fasten armature 30 securely to the bottom and sides of lever 32. This means is of particular advantage in that it permits prealignment of the armature surface in parallelism with the opposing surfaces of pole faces 24, 26 prior to hardening of the adhesive resin. I have found that the arrangement and composition above described for the elements of the electromagnetic system and the pivotal mounting of lever 32 which supports the electrode 14 provide in combination a vibratory system which is not only fast acting and positive but reliable in operation with substantially no heat transmitted to case 20, which it must be remembered, is normally supported in the hand of the operator.

By the foregoing apparatus, I believe I have provided a novel and improved hand vibrator unit of particular and inventive merit in a metal depositing apparatus of the spark discharging type. While the foregoing description has been directed toward the specific embodiment of the invention as used in conjunction with metal depositing equipment and circuitry, it is believed that the apparatus is further useful and of particular advantage in any vibrator of the electromagnetic type.

I claim as my invention:

1. In an electrical depositing apparatus of the class described, a mechanism for mechanically bringing an electrode into intermittent contact with a workpiece comprising a casing, an electromagnet mounted on said casing comprising an iron core having a pair of pole faces and a periodically energizable winding mounted thereon, a channel shaped lever, means for pivotably mounting said lever to said casing at a point spaced from one of said pole faces, an armature having a planar surface portion, means for mounting said armature within said channel shaped lever with said surface portion spaced substantially equidistant from each of said pole faces in both the unenergized and energized condition of said winding, an electrode holding means mounted proximate the end of said lever away from said pivotal mounting means and resilient means for normally biasing said lever and said armature away from said pole faces and toward said workpiece in said unenergized condition of said winding.

2. The combination as set forth in claim 1 wherein said pivotal mounting means comprises a pin, said pin journalled through a raised shoulder portion of said channel shaped lever and substantially in alignment with said planar surface portion of said armature proximate said pole faces for maintaining said spaced relationship.

References Cited UNITED STATES PATENTS 1,753,180 4/ 1930 Whittingham 335-276 X 2,373,479 4/1945 Knowles et al 335276 3,098,150 7/1963 Inoue 219-76 X FOREIGN PATENTS 474,668 11/ 1937 Great Britain.

RICHARD M. WOOD, Primary Examiner.

J. G. SMITH, Assistant Examiner. 

